Reprogramming the tumor microenvironment: endowing T with the ability to degrade the extracellular matrix 2259469

Introduction Despite the remarkable success of chimeric antigen receptor (CAR) T cell therapy in hematological cancers, the clinical experience with solid tumors has not been encouraging. Preclinical and clinical data support that the tumor-specific extracellular matrix (ECM) presents a physical barrier restricting the entry of immune cells like T cells into the tumor microenvironment (TME). ECM-degrading enzymes like heparanase and MMP7 have been explored; however, these enzymes are also associated with tumor growth, metastasis, and poor prognosis in several cancers. We focused on the collagenase MMP8 since it: (1) exhibits the best catalytic efficiency (kcat/KM) with the ability to degrade a broad range of collagens and also aggrecan, gelatins, fibronectin, and laminin, (2) MMP8 is secreted only by immune cells, and (3) MMP8 expression is not prognostic in any cancer. Methods Donor-derived T cells and second generation CAR T cells targeting CD19, HER2, and GD2 were engineered with and without MMP8. Proliferative and migratory exhaustion upon exposure to mechanical stress was evaluated in vitro. Matrigel-embedded tumor organospheroids were used to assess infiltration and cytotoxicity functions of the T cells. In vivo, xenograft models and immunohistochemistry evaluated safety, tumor rejection, and TME remodeling. Results T cells exposed to cross-linked ECM exhibited both proliferative and migratory exhaustion but this defect was rescued by secretion of MMP8. Parental T cells showed poor ECM penetration, while enzyme-expressing T cells demonstrated enhanced infiltration, migration, and tumor killing in vitro. MMP8-CAR T cells showed robust infiltration in multiple tumor models in vivo and eradicated HEY-A8 tumors and extended survival beyond 100 days, outperforming parental CAR T cells. Conclusion MMP8-engineered T cells offer a stoffer a promising strategy to overcome physical barriers in solid tumors, enhance infiltration, and unlock their full anti-tumor potential.